Photographic emulsion and process of making same.



HANS LUTTKE, OF HAMBURG, GERMANY.

PHOTOGRAPHIC EMULSION AND PROCESS OF MAKING SAME.

SPEUIFICATION formingpart of Letters Patent N 0. 722,238, dated March10, 1993.

Application filed October 16,1901. Serial No. 78,793. (No specimens.)

T0 alZluhoml it may concern:

Be it known that I, HANS LUTTKE, a citizen of Prussia, and a resident ofHamburg, Germany, have invented certain new and useful Improvements inPhotographic Emulsions and Processes of Making the Same, of which thefollowing is a specification.

My invention relates to the manufacture of light-sensitive emulsionssuch as are used for coating printing-out paper. Such papers as a ruleare coated with an emulsion containing silver chlorid, and it is Wellknown that the tint or color obtained by simply fixing the print isunsatisfactory and that for this reason a separate operation calledtoning is generally resorted to for the purpose of giving the image anagreeable tone. The toning solutions generally contain gold salts.Attempts have been made to incorporate gold salts with the emulsion, sothat the prints might be fixed at once without a separate toningoperation. These attempts, however, have so far failed to accomplish athoroughly satisfactory result.

I have made extensive experiments, and as a result of this investigationI have come to the conviction that the reason of the failure experiencedso far is the employment of chlorids, either of gold alone or gold inconnection with alkalies. When such salts are used, the chlorin combineswith the silver, and a gold compound is formed and precipitated which isnot available for toning purposes. I have found that gold compoundscontaining no chlorin are required to avoid the defects hithertoobserved and that the following substances are particularly well suitedfor the intended purpose: auryl sulfate, (Au OH.HSO auri nitrate nitricacid, Au (N0 +HNO +3H O, as well as the alkali double salts of thesecompounds, and principally the double salt of lithium. When employingemulsions containing these gold salts, an image is produced whichconsists not only of reduced silver, but also of reduced gold. Thetoning process therefore takes place simultaneously with the printing,and subsequent toning such as now practiced is dispensed with.

I find that the best results are obtained if the emulsion contains aproportion of silver chlorid equal to from thirty to fifty per cent. ofthe entire quantity of silver. I find that the reduced silver which hasbeen produced by exposing to light mixtures containing silver chlorid,silver nitrate, and silver citrate has in a very high degree theproperty of reducing gold.

As an example of my invention I will give the following receipt for anemulsion: (A) Celloidin collodion, four per cent, six hundred and twentycubic centimeters; ether, 0.720, one hundred cubic centimeters; alcohol,ninety-six per cent, thirty cubic centimeters. (B) Silver nitrate,twenty-five grams; water, twenty-five cubic centimeters; alcohol, onehundred and twenty cubic centimeters; gold and lithium nitrate, 1.4grams; auryl sulfate, 0.9 grams; lithium auryl sulfate, 1.3 grams. (0)Calcium chlorid, (anhydrous,) three grams, or lithium chlorid,(anhydrous,) three grams. (D) Citric acid, five grams; alcohol, thirtycubic centimeters.

It will be understood that the collodion is used as a binder and thatinstead of this I may employequivalent substances, as gelatin, albumen,and starch.

I may employ gold nitrates or sulfates, as hereinbefore described, asequivalents, and while in the claims I refer to the sulfates only Idesire it to be understood that the employment of a gold nitrate is tobe considered covered as an equivalent.

Having described my invention, What I claim, and desire to secure byLetters Patent, 1s

1. The process of producing photographic emulsions, which consists inadding a gold sulfate to an argentic emulsion.

2. The process of producing photographic emulsions, which consists inadding a gold sulfate to an argentic emulsion and chemically binding tochlorin from thirty to fifty per cent. of the total amount of silvercontained in the emulsion.

3. An argentic photographic emulsion, said emulsion containing a goldsulfate.

4. An argentic photographic emulsion, said.

emulsion containing a gold sulfate and having from thirty to fifty percent. of the entire silver contents chemically combined with chlorin.

HANS LUTTKE. Witnesses:

E. H. L. MUMMENHOFF, OTTO W. IIELLMRIOH.

